- Fix setting of MK_GSSAPI option by bsd.own.mk; its value should

default to the value of MK_KERBEROS unless set explicitly by
  WITH_GSSAPI/WITHOUT_GSSAPI.  (This introduces another type of
  MK_* variables which itself is questionable.)

- Teach tools/build/options/makeman script that generates the
  src.conf(5) manpage about the new type of MK_* variables.

- Fix broken logic in lib/Makefile.

lib/Makefile

@@ -62,12 +62,8 @@ _libbluetooth=	libbluetooth
 _libsdp=	libsdp
 .endif
 
-.if ${MK_KERBEROS} != "no"
+.if ${MK_GSSAPI} != "no"
 _libgssapi=	libgssapi
-.else
-.if ${MK_GSSAPI} == "yes"
-_libgssapi=	libgssapi
-.endif
 .endif
 
 .if ${MK_IPX} != "no"

share/mk/bsd.own.mk

@@ -381,7 +381,6 @@ MK_${var}:=	yes
 #
 .for var in \
     BIND_LIBS \
-    GSSAPI \
     HESIOD \
     IDEA
 .if defined(WITH_${var}) && defined(WITHOUT_${var})
@@ -479,6 +478,27 @@ MK_${var}_SUPPORT:= no
 MK_${var}_SUPPORT:= yes
 .endif
 .endfor
+
+#
+# MK_* options whose default value depends on another option.
+#
+.for vv in \
+    GSSAPI/KERBEROS
+.if defined(WITH_${vv:H}) && defined(WITHOUT_${vv:H})
+.error WITH_${vv:H} and WITHOUT_${vv:H} can't both be set.
+.endif
+.if defined(MK_${vv:H})
+.error MK_${vv:H} can't be set by a user.
+.endif
+.if defined(WITH_${vv:H})
+MK_${vv:H}:=	yes
+.elif defined(WITHOUT_${vv:H})
+MK_${vv:H}:=	no
+.else
+MK_${vv:H}:=	${MK_${vv:T}}
+.endif
+.endfor
+
 .endif # !_WITHOUT_SRCCONF
 
 .endif	# !target(__<bsd.own.mk>__)

tools/build/options/WITHOUT_GSSAPI

@@ -0,0 +1,2 @@
+.\" $FreeBSD$
+Set to not build libgssapi.

tools/build/options/WITH_GSSAPI

@@ -1,4 +0,0 @@
-.\" $FreeBSD$
-Set to build libgssapi when
-.Va WITHOUT_KERBEROS
-is set.

tools/build/options/makeman

@@ -49,7 +49,7 @@ show()
 main()
 {
 
-	trap 'rm -f _config _config2 _deps' exit
+	trap 'rm -f _defcfg _config _config2 _deps _deps2' exit
 	ident=${ident#$}
 	ident=${ident% $}
 	fbsdid='$'FreeBSD'$'
@@ -134,7 +134,7 @@ The following list provides a name and short description for variables
 that can be used for source builds.
 .Bl -tag -width indent
 EOF
-	show settings |sort >_config
+	show settings |sort >_defcfg
 	show options |
 	while read opt; do
 		if [ -f ${opt} ]; then
@@ -146,8 +146,8 @@ EOF
 			echo "no description found for ${opt}, skipping" >/dev/stderr
 			continue
 		fi
-		show settings -D${opt} |sort >_config2
-		comm -13 _config _config2 |grep -v "^${opt}$" >_deps
+		show settings -D${opt} |sort >_config
+		comm -13 _defcfg _config |grep -v "^${opt}$" >_deps
 		if [ -s _deps ]; then
 			cat <<EOF
 When set, it also enforces the following options:
@@ -159,6 +159,17 @@ EOF
 .It
 .Va ${opt2}
 EOF
+				show settings -D${opt} $(
+				    echo ${opt2} |
+				    sed -e's/^WITHOUT_/-DWITH_/' -e's/^WITH_/-DWITHOUT_/'
+				) |sort >_config2
+				comm -13 _config _config2 >_deps2
+				if [ -s _deps2 ]; then
+					cat <<EOF
+(can be overridden with
+.Va $(cat _deps2) )
+EOF
+				fi
 			done
 				cat <<EOF
 .El